md-select with ngModel requires name attribute (hasValue error)

[kmturley]

Bug, feature request, or proposal:

This is a bug with the documentation not matching expected behaviour

What is the expected behavior?

No error when copying guide code

What is the current behavior?

You get an error:
MdSelect.html:1 ERROR TypeError: Cannot read property 'hasValue' of undefined
at Object.View_MdSelect_0.co [as updateDirectives]

What are the steps to reproduce?

Following the guide, and copying example code should render without errors:
https://material.angular.io/components/select/overview

<md-select placeholder="State" [(ngModel)]="myState">
   <md-option *ngFor="let state of states" [value]="state.code">{{ state.name }}</md-option>
</md-select>

What is the use-case or motivation for changing an existing behavior?

The error is not useful, also modifying the example code, adding a name attribute to the md-select element fixes the issue:

<md-select placeholder="State" [(ngModel)]="myState" name="states">
   <md-option *ngFor="let state of states" [value]="state.code">{{ state.name }}</md-option>
</md-select>

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Angular 4.0.2
Angular Material 2.0.0-beta.7
MacOS 10.12.5
TypeScript 2.0.0
Chrome 59.0.3071.109

Is there anything else we should know?

The other example is correct here:
https://material.angular.io/components/select/examples

[willshowell]

It works fine here without the name attribute. Can you reveal more about your setup?

As a note: Typescript 2.2 is required (not sure if it's noted anywhere in the docs or is relevant here)

[crisbeto]

The name requirement on elements with ngModel comes from @angular/forms and only applies if the element is inside a form.

[kmturley]

ah yes, can that be outlined in the guide? I would guess it's a common use case

[crisbeto]

I'd say the message is helpful enough since it gives an example of how to solve the error. I'll submit a fix so Material doesn't throw any extra errors that may cause confusion.

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